1. Field of the Invention
This invention pertains to systems for pneumatic conveying material through pipelines, and more particularly to a valve for diverting the flow from one line to another.
2. Description of the Prior Art
Diverter valves has been used in pneumatic conveying systems for diverting flow from one conduit or line to another.
There are several of the rotating plug type valves which have elements that rotate in a housing within close clearances and have sealing means around matching ports. If the clearances are close enough to prevent leaking, the valve is subject to seizing in use. If the clearances are opened up, then the valve is subject to leakage of product through the clearances, and possible jamming when a particle lodges in the clearance space. These valves cannot be used on high pressure applications either. Examples of this type of valve are shown in U.S. Pat. Nos. 3,199,537; 3,489,178; 4,264,244; and 4,449,863.
Another commonly used valve is the paddle type, which has a shaft rotatably mounted at the junction or confluence of the two branch lines and a valve paddle attached to the shaft. The paddle of the prior art devices is elongated and shaped like a half ellipse, and in its two positions it rests against opposite, inner surfaces of the housing to divert flow into branch lines or conduits. Resilient material attached to the paddle or to the inner surface of the housing is used for effecting a seal. Because of its part ellipse shape, the corner where the ellipse shape meets the shaft mounting the paddle is a dead spot as far as sealing and can withstand only low pressure before leaking. Replacement of worn parts also is a problem and thus service life is limited. Examples of this type of valve are U.S. Pat. Nos. 3,384,421 and 3,773,062.
Both types of valves mentioned above can only be used effectively at pressures of about 25 psig or below.
There are also pivoted paddle type valves with a paddle that has a double sealing member sealing against a circular seat for use primarily in liquid systems. In these valves normally only the sealing member or the seat are replaceable, but not both members. Normally, the seal and seat joint are formed by flat faces that easily may be held apart by small particles that lodge on one of the faces. These type of valves do not have a smooth flow through valve and they have deep recesses or pockets formed in the valve housing and there is direct impingement of stream flow against the seat. Examples of this type of valve are shown in U.S. Pat. Nos. 260,490; 271,491; 752,439; 778,778; 1,040,548; 1,480,070; 2,035,747; 3,636,980; and 4,450,867.